Two-panel or multi-panel insulating glass composite systems consist of two or more glass panels which are arranged parallel to one another and which are joined at their edges in such a way that the gap between the panels is sealed off from the ambient air so that it cannot be penetrated by moisture. In addition, the edge seal is designed in such a way that it is able to withstand all the mechanical and chemical stresses caused by varying climatic conditions. In many cases, the gap between the panels is filled with dry gases which increase heat or sound insulation in relation to the normal air filling. Insulating glass of the type in question is mainly used in the building industry, but also in vehicle manufacture.
The edge seal of such insulating glass can be formed in different ways. In what is still the most common version, a hollow aluminium or steel profile acts as a spacer for the required gap between the glass panels. It is arranged near the edges of the glass panels so that the spacer together with the edges of the glass panels forms an outwardly facing channel for accommodating sealants and adhesives. These sealants and adhesives provide the insulating glass assembly with sufficient strength. In high-quality insulating glass systems designed to meet modern standards, a sealant acting as a barrier against water vapor is arranged between those surfaces of the spacer which face the glass panels and the surface of the glass. Thermoplastic formulations based on polyisobutylene and/or butyl rubber are generally used for this purpose. The production of such insulating glass assemblies generally involves a number of complex steps and is still very expensive despite the high degree of automation found in large production lines. Accordingly, numerous attempts have been made to simplify the complex steps involved in the production of insulating glass and, in particular, to eliminate the need for pre-profiled spacers.
In the so-called Biver system, for example, a thermoplastic strand, which is preferably based on polyisobutylene or butyl rubber and which may contain a molecular sieve to absorb moisture, is first extruded onto one panel around its edges. The second panel is then positioned over the first, after which the two panels are pressed together to the predetermined distance. The outer edge region is then sealed by a generally two-component adhesive/sealant. This system is described in numerous patents/applications, for example in DE-C-2555381, DE-A-2555383, DE-A-2555384 and in EP-A-176388 or EP-A-714964.
In order to facilitate flexible coupling of the panels and to obtain a dimensionally stable, self-supporting assembly, WO 94/16187 proposes the use of shaped bodies of a textile as the spacer between the glass panels. The textile spacer contains highly elastic but rigid link filaments and is impregnated with a resin as binder to form the edge seal. To this end, the edge of one panel is covered with the resin-impregnated textile spacer. The second panel is then placed exactly over the first, after which the two panels are pressed together to join them at their edges. After the press has been opened, the reactive binder system is left to cure.
WO 97/31769 describes a preformed flexible laminate for forming the edge seal between insulating glass panels. This flexible laminate contains a wavy flat material partly or completely embedded in its core material as spacer, its surface extending perpendicularly of the glass panels. On at least one surface, the laminate has a polymeric coating which seals off the interior of the panel assembly against air and/or moisture and maintains the required distance between the glass panels. Laminates of the type in question are produced by a multi-step co-extrusion process in which the wavy flat material is first embedded in a core material which then has to be coated with one or more polymeric materials on its outer surfaces.
According to EP-A-81656, two-panel insulating glass is produced by first coating the edges of the glass panels to be joined with a solution of a primer or adhesive. The glass panels are then brought to the predetermined distance apart and a thermoplastic resin composition of a butyl rubber and a crystalline polyolefin, which may also contain tackifiers and drying agents, is extruded into the edge region.
The disadvantage of all the above-mentioned edge sealing systems based on thermoplastic polymers lies in their poor heat resistance and long-term temperature resistance. These disadvantages can only be overcome by using reactive systems of the reactive hotmelt adhesive type which post-crosslink either thermally or under the effect of moisture or oxygen so that a crosslinked polymer matrix around the edge of the insulating glass system provides for adequate thermal stability. Thus, WO 97/15619 describes sealants/adhesives for the production of insulating glass units based on one-component, hot-applied, chemically crosslinking adhesives/sealants. These binder systems contain a thermoplastic hotmelt adhesive resin mixed with a resin which can be crosslinked with atmospheric oxygen and/or moisture. The hotmelt adhesive resin acts as a fusible component during the original application and establishes early strength immediately after cooling. The crosslinkable polymer phase then begins to react by crosslinking with the oxygen or moisture in the surrounding air. The crosslinkable resins mentioned include moisture-reactive polyurethanes, moisture-reactive polysulfides, polydimethyl siloxanes or oxygen-curing polysulfides.
DE-A-19821356 describes a process for the production of a silane-modified butyl rubber in which a butyl rubber is reacted with a mercaptofunctional silane containing hydroxy groups or hydrolyzable groups in the presence of a radical former. According to the teaching of this document, such polymers can be mixed with other additives in a kneader, processed to form a two-component composition and applied to glass by means of a suitable machine. The applied composition then acts simultaneously as a spacer for the two glass panels, contains a drying agent for the inter-panel gap and acts as a water vapor and gas barrier and as an elastic bond.
WO 97/48778 describes a hotmelt adhesive composition containing a mixture of at least one reactive binder based on silane-functional polyisobutylenes, hydrogenated polybutadiene and/or poly-α-olefins and a non-reactive binder from the group of butyl rubbers, poly-α-olefins, polybutenes, styrene block copolymers or diene polymers. These hotmelt adhesive compositions may be used as one- or two-component adhesives/sealants for the production of insulating glass. There is no need for separate spacers of metal or plastic profiles.
Besides some processing-related advantages, the various systems described in the foregoing have certain disadvantages. The Biver system requires a thermoplastic spacer (TPS) and a conventional, generally two-component adhesive based on polysulfide, silicone or polyurethane. Although, in the case of reactive hotmelt adhesives, only one material is generally required, both the above-mentioned binder systems are supplied in drums from which the material is pumped to the point of application, optionally after heating. Problems can arise during processing if, in cases where the volume of material called up per unit of time is high, the quantity melted in the reservoir of the applicator and the melting rate per unit of time are not sufficient to guarantee the necessary flow of material. In addition, the reactive one-component warm- or hot-melting systems are attended by the problems familiar to the expert, such as difficulties during packaging, poor stability in storage and a low curing rate and during the disposal/cleaning of the used adhesive-contaminated containers.
Against the background of this prior art, the problem addressed by the present invention was to provide a binder system which would lend itself to application in the same way as reactive hotmelt adhesives, but which would provide for improved storage, feeding and transportation in relation to the prior art. In particular, the binder system would be easy to handle and to dose, even after prolonged storage at various temperatures. This would also include avoiding contamination of the transit containers. In addition, the reactive components would lend themselves to rapid melting and mixing. Neither the adhesive properties nor the water vapor and gas barrier effect would be adversely affected.